Aspects of the Exxon Valdez Oil Spill--a Forensic Study and a Toxics Controversy

ABSTRACT

After the Exxon Valdez oil spill in Prince William Sound in March, 1989,
much work has been done to track the spilled oil and study its fate and its
affect on the environment. Our studies involved developing and applying methods
to identify and track the spilled Exxon Valdez oil (EVO) as it weathered,
as well as to differentiate it from other petrogenic hydrocarbon input sources
in PWS. Application of these methods to the study area has yielded two important
findings. First, it was discovered that not all the oil or tar on the beaches
was EVO. Instead, tarry residues of oil from the Monterey Formation, Southern
California, also were prominent on some of the Prince William Sound beaches
along with EVO. Monterey Formation oil was used in the early development of
Alaska, before the discovery of North Slope Crude, and most likely was disbursed
throughout the Sound from the port of Old Valdez in the Great Alaskan Earthquake
of 1964. The second study also involves differentiating petrogenic sources.
A third petroleum input source to PWS, namely natural oil seeps in the Gulf
of Alaska, has been claimed by others to contribute a substantial, and potentially
toxic, polycyclic aromatic hydrocarbon (PAH) background to the Prince William
Sound benthic sediments. If this claim is true, it would have the effect of
mitigating the long-term effects of the oil spill. Our studies and cooperative
work with NOAA provide evidence that it is coal and not oil that contributes
this PAH background. Unlike the case with oil, PAHs in coal would not be bioavailable
and thus would be considered contaminants but not pollutants capable of causing
adverse effects on exposed biota. Resolution of the source of the PAHs is, therefore,
an important environmental issue.

This work in identifying petroleum sources, both natural and anthropogenic,
has a great deal of transfer value to other estuarine systems. The geochemical
information obtained in Prince William Sound can be extrapolated and applied
to the study of oil residues on the California coastline and in San Francisco
Bay. Current studies are attempting to correlate or differentiate spills in
these two areas and sort out the origin of the petroleum input sources.